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Zur Stereochemie der 3-Oxo-5-phenyl-1-cyclopentancarbonsäuren, 5. Mitt. Zur stereoselektiven Synthese der stereomeren 5-Phenyl-dihydroisosarkomycine
Authors:August W. Frahm
Abstract:Stereochemistry of 3-Oxo-5-phenylcyclopentanecarboxylic Acids, V: On the Stereoselective Synthesis of the Stereomeric 5-Phenyldihydrosarcomycines In connection with our attempts to synthesize stereoselectively the 5-phenyldihydroisosarcomycines 1–4 , the C-methylation of 3-oxo-t-5-phenyl-1,1,r-4-cyclopentanetricarboxylic acid trimethylester (5) was performed. The reaction yields t-4-methyl-3-oxo-c-5-phenyl-1,1,r-4-cyclopentanetricarboxylic acid trimethylester (7) with a high degree of stereoselectivity. The stepwise degradation of 7 by acidic or basic saponification and decarboxylation has been examined. Via the isolated intermediates t-1,t-4-dimethoxycarbonyl-c-4-methyl-3-oxo-t-5-phenyl-r-1-cyclopentanecarboxylic acid (10) and c-4-methoxycarbonyl-t-4-methyl-3-oxo-c-5-phenyl-r-1-cyclopentanecarboxylic acid (12) the acid 1 (t-4-methyl-3-oxo-c-5-phenyl-r-1-cyclopentanecarboxylic acid) was obtained stereoselectively. The trans-carboxylic acid (c-4-methyl-3-oxo-t-5-phenyl-r-1-cyclopentanecarboxylic acid) (3) is accessible by thermodynamically controlled rearrangement.
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